Comparative Studies On Growth Characters And Source-sink Relationships Of Different Types Of Ratooning Rice

In 2004～2005, four field experiments about cultivars comparing, stubble height,node-cuttage and sowing by stages were designed to study the differences in source andsink characteristics of ratooning rice among different cultivars (hybrids), effects ofstubble height on source and sink characteristics of ratooning rice, differences in sourceand sink characteristics of ratooning rice from different nodes and those betweenratooning rice and its same-term tasselling main crop. The main results were as follows:1. As for yield of ratooning rice, Peiliangyou 210 and Peiliang E32 were highestrespectively in 2004 and 2005. As for the total yield of main crop and rationing rice, thehigher three cultivars were Peiliangyou 981, Peiliangyou 210 and Peizashuangqi in2004, and they were Peiliangyou E32, Peiliangyou 981 and Shanyou 63 in 2005. Underconditions in this study, the optimum cultivar for ratooning in Changsha region wasPeiliangyou E32, and Peiliangyou 981, Shanyou 63, Peiliangyou 210 and Peizashuangqiwere in the next places. Peiliangyou 210 was a perfect variety for ratooning cultivationwith the lower stubble height. Rice quality of ratooning rice was better than that of maincrop slightly, but it was inferior to that of the same-term tasselling main crop. That wasto say, rice quality of ratooning rice was intervenient between that of early rice and laterice.2. There existed many differences between hybrid and normal (male parent) ricesin many aspects: compared to male parent, LAI, angles of the top three leaves, rootactivity and yield of main crop of hybrid rice were higher, whole duration of hybrid ricewere shorter in main crop and longer in ratooning rice, regeneration of axilary buds ofhybrid rice was quicker and the stage of appearance of maximum LAI was earlier. Theratio of grain numer to leaf area in main crop and ratooning rice showed hybridrice＞male parent trend, but the specific leaf weight showed the opposite trend.3. The optimum varienties for ratooning cultivation should take on the followingcharacteristics: moderate growth duration, compact plant type, higher root activity, LAIand chlorophyll content, more grain number per panicle and higher 1000-grain weight,moderate ratio of grain numer to leaf area, moderate dry matter weight at maturity andhigher harvest index, lower photosynthesis rate in prophase of filling stage but higher inthe anaphase, more big vascular bundles in the 1st intemode from the top, bigger area of big vascular bundle in the 3rd intemode from the top, higher catalase activity in branchof panicle at full heading stage, more residual photosynthesis outcome in stems andsheathes at maturity and most of them be stored in intemodes below of the 2nd from thetop.4. Stubble height affected source and sink characteristics of ratooning riceprominently. By decrease of stubble height, plant height, spike length and grain numberper panicle were increased but effective panicle number, seed setting percent,1000-grain number and yield were decreased. The sink limitation to lower-stuubleratooning rice was slightly greater than that to higher-stuuble ratooning rice, but thesource-sink relationship of ratooning rice was source-limited in despite of stubble height.Soluble sugar content in stem and sheath was dcreased by decrease of stubble heightcommonly, and translocation rates of starch in stem and sheath in middle and higherstubble treatments were higher than that in lower ones. The higher stubble height thelower endogenesis GA₃ and IAA content in axillary buds, and GA₃ and IAA content wasrapidly increased by decrease of stubble height, which showed stubble height affectedon regeneration of axillary buds by effect on endogenesis hormone content.5. Evident difference in source and sink characteristics existed between ratooningrice and its same-term tasselling main crop. Comparing to main crop, seed settingpercent was higher slightly, 1000-grain weight was lower slightly, specific leaf weightwas higher and the ratio of grain number to leaf area was heightened one time inratooning rice. If looked value of different charaters of main crop as 1 respectively, thenLAI and laf area per culm were 1/8～1/5, dry matter weight per hill was 1/4～2/5, grainnumer per panicle and yield were about 1/3 in ratooning rice. Comparing to main crop,photosynthesis rate was higher, crop growth rate was lower but net assimilation rate washigher 2～5 times in ratooning rice. As for assimilation outcomes of flag leaf, 2/3 ofthem were translocated to panicle and about 1/4 of them residued in stems and sheathesin main crop, but in ratooning rice, above 4/5 of them were translocated to panicle andthe percent of residue in stems and sheathes was evidently lower than that of main crop.Tranlocation percent of starch in stem and sheath in ratooning rice was lower than thatin main crop, but the tranlocation percent of solube sugar showed the opposite trend. Asfor source-sink relationship, main crop belonged to sink-limited, and ratooning ricebelonged to source-limited but sink increase also had yield-increasing effect in someextent.6. In matrix condition (in vivo), plant height, leaf area per culm, painicle length,grain number per panicle of ratooning rice were increased, and seed setting percent andthe ratio of grain number to leaf area of ratooning rice were decreased with the decline of node position. Plant height, leaf area per culm, painicle length, grain number perpanicle of ratooning rice in vitro were bigger than those in vivo, and the differenceamong different nodes was greater in vitro. The difference in endogenesis hormone inaxillary buds existed between in vivo and in vitro: Contents of GA₃ in axillary buds andIAA in higher node axillary buds on the 9th d after node-cuttage were higher than thoseof 40 cm stubble height treatments; Contents of GA₃ and IAA in higher-node buds werehigher than those in lower-node buds in vitro, but those in lower-node buds were higherin vivo; Content of CTK in axillary buds was decreased rapidly in 9 d～15 d afternode-cuttage, but there showed trend of lower-node buds＞higher-node ones in thisstage.